Breaking news from the Voith Damper Front

Having researched, reverse engineered, and rebuilt my Voith damper about 5 times in the last 6 months now, I have some interesting news to report.

MOST IMPORTANT: I have identified the single point of failure that leads to all the other problems: the "teflon" thrust washer. Any time you re-pack your damper, you need to check that your thrust washer is still doing its job. What is its job? Glad you asked. Its job is to do two things: 1) Securely locate the inner drive disk's bearing in that bearing's cup, the precision ground steel hub riveted to the rear half of the damper shell. 2) Create a seal between the drive disk and the front half of the damper shell.

What happens if it is worn to an under size dimension? Glad you asked. 1) The drive disk starts moving longitudinally relative to the shell. 2) The drive disk starts "wobbling" relative to the shell. 3) The bearing cup is marred allowing more wobbling. 4) The inner and outer drive shafts move relative to each other. 5) Causing the triple seals to get compressed and leak trans oil. 6) That can now enter the shell through the gap between the thrust washer and the shell, dilute the grease, causing it to be expelled from the shell as it runs past the seal when you shut down.

BUT WAIT, IT GETS WORSE!

The clearance between the hydraulic flanges, (What!? What are those? OK, the hydraulic flanges are the 12 asymmetrical spacers located between the front shell and the hydraulic pin, (round spacer), and between the hydraulic pin and the rear shell, held in place by the bolts that bolt the flywheel to the damper. I call them hydraulic whatevers, because as it turns out they are the key to the hydraulic damping action of the damper. More on that later.

Anyway, the clearance between the flanges and the drive disk, is only about 0.018" on the top and bottom. So what happens if the wobble gets to be more than the almost nothing permitted by that tiny clearance, is that the the drive disk hits the flanges. They are hard steel, about the same hardness as the drive disk, so as the drive disk hits them neither one gives. The disk just "bounces" off and wobbles harder. What does give, are the "stakes" where the drive disk's central hub is staked to hold the outer disks precisely level so that they are rotating true and don't hit the flanges. Only now they are not.

So, how do you check your thrust washer? Glad, aw never mind the smarmy BS. Anyway, here is what you do: completely disassemble and degrease your damper. Reassemble it without any grease or springs or spring holders or plastic parts. You don't have to use all six bolts - I just use 3. And you don't have to bolt the bolts to the flywheel - I just use some nuts instead of the flywheel. Now pick up you damper and shake it. If your washer is still good, you won't hear any rattling. If you do hear rattling, please write me as I am getting ready to go into production on new thrust washers and I need to speak to everyone who has symptoms so that I can start to get an idea how much variance there is between different dampers.

So, that is the important stuff, but that is not all I have learned. There is grease on the market that will replace Kluber and cost 1/3 or less of what we pay. No cold starting or hot starting issues at all. Excellent damping. However what I learned about how the damper works is that as it is oscillating to smooth the engine's power impulses, the round pins are moving through the grease that is pressed against the inner wall of the shell by centrifugal force. That movement through the grease is exactly analogous to the movement of shock oil through a valve. That resistance is how the damper damps. The reason the flanges are asymmetrical is so the flanges protrude into the grease channel area where pins are moving. This makes for more resistance as the channel is just a bit narrower due to the protruding flanges. That is why you put the flanges in so that they are pointing clockwise, so that the more resistance side of the pin's movement will be as it is moving to counter-clockwise, i.e. in the same direction the engine's power pulses are applied.

For this reason, until I can do an A to B comparison on the damping of an in-spec damper (mine is not, but I may have another one, supposed to be undamaged, coming soon to use for testing.) using Kluber vs. the grease that I have located, I recommend that you stick with Kluber, as it is tantamount the oil in a shock, and you want the precise viscosity characteristics. The only exception would be if you want to test build your damper and know that you will soon be repacking it. Then there is no reason to waste money on Kluber. Write me, I have a tub of the substitute, and will send you 400 grams for $40 and that includes postage.

What else? Well, if you have a damper that has gotten damaged, and still makes noise after you repack it, write me. I am building the tools and procedures to repair them. So far I have made some jigs with which to re-stake the drive disk. Mine is going to need more extensive operations, but that may be all your's needs.

Last but not least, here is a bit of pie-in-the-sky: I am going to contact Voith to see if it might be possible to commission a run of their new style dampers sized to fit 348s and ts. They are supposed to be wear-proof, and the damping action is more precisely engineered. Don't hold your breath on that one

Looking forward to hear if anyone needs a new thrust washer or if you checked and yours is still good! I have no idea if they normally wear, of if mine was just a fluke, or more likely the result of running dry for quite some time.

Does any of this apply to the Voith damper in the 355? Not sure. Certainly the design of the 355's damper is more like the modern Voith damper which according to Voith is "wear-free". Still I have seen pictures of 355 dampers all empty of grease, so I believe that they fail also, but I still don't know if they have a thrust washer that might wear and be the key point of failure.

 

Thanks!

If anyone wants to test their thrust washer and their grease is still relatively fresh, here's a shortcut. You take the top off the damper. Then using a small spatula like a plastic putty knife, you scrape out the grease and scrape it off into a bowl. I do this on a table top with an opened up plastic bag taped to the top. Once you get enough of the grease out of the way, lift each of the springs and associated plastic parts out as a unit with the grease holding it all together and set them on the plastic. No need to clean your springs as they are not needed for the test. The use the spatula to clean as much as possible of the grease off the drive plate and shell halves. Keep the grease in your bowl, and you can reuse it, along with the grease that adheres to the springs.

Once you've scraped as much as you can, then you do your standard clean up on the shell halves, drive plate, flat spacer flanges, and round spacers. It's a lot easier if you scrape first.

 

I don't understand why you think the bushing is useless. The "plate" in the center of the housing's shell is located longitudinally by that bushing on one side, and by the bearing on the other side. My old damper had melted the bushing, so the result was that the plate could move longitudinally. In order to test this you have to remove most of the grease, and remove the springs along with their locator pieces, (what you call "bushings"), and then test assemble the damper without the springs, using nuts and bolts to clamp the two shell halves together. I don't remember exactly how I tried to move the plate - maybe I shook the housing. Anyway, I could definitely detect movement. I shimmed the bushing and the movement went away. Then I got a good used clutch from GT Car Parts with an unmelted damper. I had the clutch relined and the clutch plates surfaced. Before I assembled the new clutch, I tested the damper for longitudinal movement: none.

Still had problems though: Turns out though that the noise that caused all this turmoil was not the damper, but the splined output shaft from the clutch that drives the transmission. I had my transmission rebuilt by the esteemed rifledriver, he had the splined shaft welded to the drop gear, and the noise went away. I think that once the whole assembly is not vibrating, the triple seals will last much longer. I need to replace my triple seals one last time to test this theory. That's a ways off as I have a bunch of other issues to deal with first. We'll see...

As for replacement locater pieces, you make a good point, that we need a supply of repleacements. I am going to be working with a 3d printer soon, and will try to duplicate them, although if anyone else wants to try, please go ahead as I have one other project that comes before even Ferrari parts!

 

Sorry, as for balancing, I don't know what to tell you about that. With all that grease moving around in there, not sure it's that important. I have read claims that the grease actually balances the assembly. I have not been able to verify those claims and I have serious doubts about them, but I haven't been able to disprove them either, although my thought experiments indicate that the idea has many flaws in general. Still, in the specific case of the Voith damper when filled with Kluber grease, the grease may actually serve to balance close enough for this use case.

 

You are missing the point here: the bushing is for *longitudinal* positioning. Take the bushing out of the shell half. Assemble the damper without grease and springs, bolting it together with nuts and bolts instead of screwing the bolts into the clutch plate. Pick it up and shake it along the axis of rotation. You will hear the inner plate slopping back and forth. Taking that slop out is the purpose of the bushing.

You are correct - I forgot about the words in the manual. Still, that grease moves around, and is a lot heavier than the balance spec. so, again, I am not sure how critical the balance is... This may be a case along the lines that Subarubrat brings up.

 

I is hard to explain with words - how frustrating as I know that if I was standing in front of you holding the parts in my hands I could show you in 5 seconds.

Anyway, let me try again. First: yes, I mean in line with the axis of rotation. Think of it this way: the damper is like a hollow shell split down the middle. Inside that shell is the "platter" that oscillates back and forth and whose oscillations are constrained by the springs and damped by the grease. The platter has a bearing on one side that sockets into the back half of the shell. But what prevents the platter and its bearing from moving forward, yes, in the same movement that you get when you force it out using bolts through the grease holes? The answer is the round "teflon" bushing (it is a plastic like teflon, but capable of withstanding higher temps) in the front half of the shell. On my damper, that bushing had gotten somewhat melted so it was no longer the proper thickness, and therefore no longer held the bearing snug in its socket. When the bearing is not snugly socketed, the platter will wobble, just a tiny bit, but that tiny bit is enough to compress the triple seals allowing extra oil to escape the trans and contaminate the damper grease more quickly than expected, with complete meltdown to follow, sooner or later.

 

As far as it being worth the trouble, I think so. Now that I have a fully functional damper, I really appreciate the smoothing of the power pulses that allows one to drive at low revs. Of course, my car is a Mondial t Cab, so being able to drive it like a caddy on a smooth road in good weather with the top down is part of the charm - knowing all the while that all one needs to do is drop it two gears, and it's right back to track flavor.

 

I'll be on vacation for the next week, but get back to you after that.